Washington: A Secret Service agent shot and critically wounded a man Friday afternoon who approached a guard booth outside the White House and refused to put down the small pistol he was carrying, according to law enforcement officials.

Lines of tourists were frantically ushered away from the area as heavily armed police converged on a nearby security shack, which is outside the secure perimeter and accessible to the public. The White House was put on lockdown, and Vice President Joe Biden was secured inside the complex, authorities said. President Barack Obama was golfing at Joint Base Andrews at the time.

Authorities said the man, who was shot once in the chest, was hospitalised in critical condition Friday night. Two law enforcement officials identified him as Jesse Olivieri, a Pennsylvania man in his 30s. His relatives could not immediately be reached to comment.

Police released no other details about him or an apparent motive. Authorities discovered ammunition for a .22-calibre weapon inside the man’s white, four-door sedan, which was parked near the scene, according to two law enforcement officials.

Friday’s apparent attempt to breach the White House grounds is another in a series of security incidents in recent years at or near the presidential complex. It took place against a backdrop of heightened global tension brought on by terrorist attacks and the ongoing wars in the Middle East and Afghanistan and as officials were investigating the crash of an Egyptian passenger jet over the Mediterranean Sea.

Law enforcement officials said there was no immediate sign that Friday’s incident, which occurred just after 3pm, had any links to terrorism.

The Secret Service said in a statement that the man approached the security gate holding a gun and that “officers gave numerous verbal commands for the subject to stop and drop the firearm. When the subject failed to comply with the verbal commands, he was shot once by a Secret Service agent and taken into custody.”

Officials said they recovered the man’s firearm.

Federal agents with the Washington field office of the Bureau of Alcohol, Tobacco, Firearms and Explosives were helping to trace the weapon, according to an agency spokesman.

Law enforcement officials noted that the man did not gain access to the White House complex.

People have tried to reach the mansion’s grounds for years for a wide variety of reasons. Some suffered mental illness, others wanted to make a political statement and some sought notoriety. One person this year allegedly climbed the fence to try to escape apprehension in a series of robberies he had just committed.

The Secret Service last year added small spikes – or “pencil points” – to the top of the 1.8 metre fence that surrounds the White House complex after a series of incidents in which intruders climbed the fence. Last month, the agency announced a plan to raise the height of the security fence to 3.4 metres by 2018.

Perhaps the most serious breach was on September 19, 2014, when Omar Gonzalez climbed over the north fence and made his way deep into the White House. When he was finally tackled by an off-duty Secret Service agent in the ornate East Room, he was found to have a knife in a pants pocket. Two hatchets, a machete and 800 rounds of ammunition were found in his car nearby. Secret Service Director Julia Pierson resigned two weeks later.